# Time Conversion Calculator

## Calculator Use

Enter the time value and units you want to convert from, then choose the time unit you want to convert to. You can convert between seconds, milliseconds, microseconds, nanoseconds, days, hours, weeks, months, and years.

Months in this time conversion calculator are calculated using the average of 30.416 days per month. This is equal to 365 days per year divided by 12 months per year. 365 ÷ 12 = 30.416 days per month.

Years in this time converter are calculated as 365 days per year. This calculator does not consider the extra day in a leap year which has 366 days per year.

## How to Convert Units of Time

You can use conversion factors to convert a unit of time into another using multiplication or division. By knowing the conversion factor, converting between units can become a simple math problem:

**S * C = E**

Where **S** is the starting value, **C** is the conversion factor, and
**E** is the converted result.

## Conversions with Seconds

The table below contains conversion factors to convert any time value into seconds using multiplication.

Example: Convert 120 Minutes into Seconds

- Multiply 120 minutes by 60 seconds per minute
- 120 min * 60 s/min = 7200 seconds

Example: Convert 28,800 Seconds into Hours

- Multiply 28,800 seconds by 1/3600 hours per second
- This is the same as dividing 28,800 seconds by 3600 seconds per hour
- 28,800 s ÷ 3600 s/h = 8 hours

To convert among any units in the left column, say from A to B, you can multiply by the factor for A to convert A into seconds then divide by the factor for B to convert out of seconds. Or you can find the simplified factor by dividing the conversion factor for A by the conversion factor for B.

To convert from minutes to hours multiply the number of minutes by 60 and then divide by 3600. Simplified, this is the same as multiplying by 60/3600 which is 0.016666667. To convert directly from minutes to hours you multiply by 0.016.

Unit

Symbol

( s )

( s / Unit )

**second**

**s**

**second**

**1**

### Sidereal

*Sidereal day:** a unit of time used in astronomy, equal to the period of time in which the earth makes one rotation relative to the stars. If we could view the earth from outside the Solar System, we would see that it actually completes 366.242 rotations during one year (one revolution around the sun). We only count 365.242 because one rotation is cancelled out for us by our tour around the sun. Thus the sidereal day, the average interval between two successive risings of the same star, is shorter than the mean solar day (see day) by 1/366.242. The sidereal day equals 23 hours 56 minutes 4.090 54 seconds, or 86 164.090 54 seconds. Like the regular day it is divided into 24 sidereal hours, each sidereal hour being divided into 60 sidereal minutes and each sidereal minute into 60 sidereal seconds. The sidereal hour equals 59 minutes 50.17 seconds; the sidereal minute equals 59.8362 seconds; the sidereal second equals 0.997 270 second. Traditionally, observatories had clocks set to this sidereal cycle, and astronomers still use sidereal time in making telescope settings.*

From --
*How Many? A Dictionary of Units of Measurement* at http://www.ibiblio.org/units/ accessed 2023-07-25.

## References/ Further Reading

The National Institute of Standards and Technology (NIST) -
*The NIST Guide for the Use of the International System of Units* - Appendix B, subsections
B.8 Factors for Units Listed Alphabetically and
B.9 Factors for units listed by kind of quantity or field of science.

Lide, David R., Daniel (Editor-in-Chief).
*CRC Handbook of Chemistry and Physics, 89th Edition*, New York, NY: CRC Press, p. 1-28, 2008.

Wikipedia contributors. "Conversion of units" Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, last visited 26 Jun. 2011.